1. Field of the Invention
The present invention relates to a dual clutch transmission apparatus and a start control method in which a plurality of clutches are controlled.
2. Description of the Related Art
Conventional multi-stage vehicle transmissions having a plurality of clutches enabling fast gear changes on automobiles are known (see, for example, Japanese Patent Application Laid-Open No. 58-124851).
In a multi-stage vehicle transmission disclosed in Japanese Patent Application Laid-Open No. 58-124851, a first clutch connects and disconnects an input shaft that receives the driving force of an engine to and from a first main shaft provided rotatably on the input shaft, and a second clutch connects and disconnects an input shaft to and from a second main shaft provided coaxially with the input shaft.
In this multi-stage vehicle transmission, a sub shaft connected to an output shaft is disposed parallel to the input shaft, the first main shaft, and the second main shaft. This enables transmission at a predetermined gear ratio from either the first main shaft or the second main shaft to the sub shaft through a plurality of gears by the connection of either the first clutch or the second clutch. The output shaft connected to the sub shaft is thereby rotated to output driving force.
Thus, in the above-described multi-stage vehicle transmission, the rotation speed of the output shaft is changed by selectively connecting the first clutch and the second clutch to transmit a torque on the input shaft to the sub shaft at a different gear ratio, without blocking power at the time of the gear change.
In recent years, there has been a demand for providing a motorcycle having a limited mount space with a multi-stage vehicle transmission having a plurality of clutches such as those mounted on an automobile. To mount such a multi-stage vehicle transmission having a plurality of clutches on a motorcycle, it is desirable that the transmission itself is downsized.
In a transmission, a clutch is connected and disconnected on the basis of the state of engagement between a drive-side member and a driven-side member (the relative position of the two members) and has a comparatively large weight as a member of a drive transmission system.
In an arrangement having a plurality of such clutches, the weight of the multi-stage transmission itself may be increased in comparison with a multi-stage transmission having one clutch. This leads to a need to provide a transmission itself that has a small size by reducing the size of a clutch itself.
The size of a clutch is proportional to a thermal load at which the clutch can withstand frictional heat generated in a half-engaging state (in which the clutch slips while transmitting a torque) during connection and disconnection of the clutch, particularly frictional heat generated at the start of travel upon changing from a neutral (N) position to a first gear position. That is, to have a thermal load at which it can withstand frictional heat generated in a half-engaging state, it is required to increase the sizes of the drive-side member and the driven-side member themselves which are to be half-engaged.
That is, in an arrangement in which the clutches are simply reduced in size, a multi-stage transmission cannot withstand a thermal load at the start of travel. The problem is that the multi-stage transmission requires clutches having a size that is large enough to operate under the thermal load at the start of travel and thus, the clutches become heavy.